Four bodies have been retrieved by rescuers overnight as they clear the 12 mangled coaches of a train that derailed in India's West Bengal state, raising the death toll to nine, according to a railway official.

At least 45 people were injured in the accident on Thursday as the coaches went off the rails and three capsized, said Rajiv Jain, a railroad ministry spokesman.

The rescue work was completed and the track was being cleared to restore train services in the region, Jain said on Friday.

Images from the scene after the accident showed passengers stuck in twisted metal and debris as rescuers tried to pull them out.

The train was on its way to Guwahati in Assam state from Bikaner, a city in Rajasthan state, when the accident occurred in Jalpaiguri district.

All of the injured were being treated in a hospital, senior police officer Debarshi Dutta said.

Senior railway official Guneet Kaur said the cause of the accident was being investigated. She said the government would provide financial compensation to families of the deceased and all of the injured.

Accidents are common on India's massive but ageing railway network.

Safety standards have been an ongoing concern on the state-run system, which operates 9,000 passenger trains and carries about 23 million passengers every day.

(With input from agencies)